Composition of matter and method of its preparation



Nov. 3, 1931.

c. MARTELL 1,829,998

COMPOSITION OF MATTER AND METHOD OF ITS PREPARATION Filed Sept. 27, 1928CO/VDUC'M/VCA" //V MACROMHGS P5? MOI/CAL M/Lt' DAYS MIA/[R850 PatentedNov. 3, 19 31 I 4 UNITED. STATES PATENT. OFFICE- CHARLES MABTELL, FGIOEBO, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OFNEW YORK, N. Y., A CORPORATION OF NEW YORK i COHPOSITION OF MATTERMETHOD OF ITS PREPARATION Application filed September 27, 1928. SerialNo. 308,611.

- This invention relates to compositions of matter and methods of theirpreparation, and more particularly to compositions used in electricalindustries for their insulating and other electrical properties.

The invention further relates to insulating compositions containingrubber, balata and wax or their equivalentsfwhich compositions havestabilized electrical characteristics and mechanical propertiesadaptingthem to be used for the insulation of submarine cables,

and more specifically to certain such compounds having lower dielectricconstants andlower conductance and capacitance than gutta-percha, andbeing therefore especially adapted for insulation of submarine cablesfor high frequency transmission.

The objects of the invention are to provide a composition havin in ahigh degree the characteristics desira 1e in insulating materials,especially for use under water, and to provide an insulating materialand its method of production having in a high degree the characteristicsdesirable in-cables,

particularly in cables employed for tele-' phonic communication or otherrelatively high frequency transmission.

A further ob ect 130 provide a cable in sulating material which issuperior to, and at the same time cheaper to manufacture thangutta-percha.

In accordance with one form of the invention, rubber, or similarhydro-carbon substances, balata, and Montan wax are mixed together toform the compound, each of the ingredients having been treated byspecial processes fully set forth hereinafter. The proportions of theseveral ingredients, and the precise composition of each of theingredients themselves, ma be varied consider ably and still beeflectivein securing the desired properties. i

The invention and its relation to the prior art will be understood fromthe following description, taken in connection with the attacheddrawings, in which Figs. 1 and 2 are graphical representations ofcomparative data obtained experimentally from samples of gutta-perchaand from insulating mate;

rials prepared in accordance with this inven-' tion, as will be furtherdescribed.

Gutta-percha is the only material which has been generally accepted assuitable for the insulation of submarine cables with high transmissionqualities. Various substitutes 1 for gutta-percha have been proposed,in-

cluding vulcanized rubber, as disclosed in the application of R. R.lVilliams'and A. R.

Kemp, Serial No. 678,509, filed December 4,

1923. The disadvantage of the vulcanized rubber insulation formed inaccordance with the above applicationis that it, like all rubberinsulators, must be vulcanized in. position on the conductor, and thecable core is 1 very likely to become deformed during the process ofvulcanization, unless expensive and cumbersome precautions are taken.Also, vulcanizable rubber alone is too resilient to be extruded in'anextrusion press,

which fact necessitates the inclusion in it of 7 some solid, finelydivided filler, which has the undesirable effect of raising thedielectric constant of the finished insulator. It has also beenproposedto use raw rub- --ber in admixture with vegetable waxes as a submarineinsulating compound.

Such a compound is described in United States Patent No. 699,383, datedMay 6, 1902 to Adolf Gentzsch, and it has been found that such compoundsmay possess fairly satisfactory mechanical properties. However, they arenot electrically stable, and it is for this reason that they have notbeen adopted. for use in insulating submarine cables.

In experiments with rubber for usein submarine insulating compounds ithas been found that in the unmixed, unvulcanized state, thoroughlywashed, crude rubber is not electrically stable when immersed in water.

Sheets of such rubber, during immersion in v nating or materially seawater, undergo a gradual increase of dielectric constant and decrease ofinsulation resistance upto a certain point, when sudden and almostcomplete failure of the material in respect to insulating propertiesoccurs. It appears that this sudden failure of crude rubber in water isdue to protein films which pervade the mass, forming, when thoroughlywet, paths of low electrical resistance throughout the rubber. It istherefore desirable when unvulcanized rubber is to form* in the state ofcommercial crude rubber or ble,

of uncoagulated latex, is subjected to the ac--' tion of water at atemperature above 100 C. for several hours to render the proteins solusulting product is a rubberwhich retains its ,fiuid of the tree known toinsulating and electrical properties practically unimpaired for longperiods of time whenummersed in a salt solution similar to sea water. Itis perhaps the best material at present available as an ingredient inthe composition of the present invention, but obviously any other rubberproduct having sat- I isfactory electrical and mechanical properties maybe used, although prepared by an entirely different process.

For the sake of distinctness, certainof the terms used in the presentspecification and claims are defined as follows:

Rubber.Various species of rubber such asare known as Hevea, Castilloa,guayule and others, whether in the form of latex, artificial dispersion,or in solid unvulcanized form. i

H am? warm-.A wax having melting point above 60 C. and below the hiling,point of water.

Montan wam. A bituminous hard wax obtained from lignite.

BaZata.A gum obtained from the milky biologists as the property of eplastic when Mimusops balata or globosar Tkernw-platz'city.-That matterwhich causes it to beco heated to the neighborhood of the temperature ofboiling water, and which therefore makes it possible to extrude thematter from an extrusion press while hot. This property is not possessedby ordinary riwber, but is possessed by balata, and also by thecomposition made in accordance withthis specification.

In practising one embodiment of the invention, rubber latex has beendiluted with and is then washed and dried. The reasaaeee water in theproportion of one part of latex to four parts,of water, the mixturebeing then subjected to 50 pounds steam pressure for nine hours. A 5%solution of acetic acid (1,0000. c. per gallon of undiluted latex) wasthen added to coagulate the latex, and the water. was then removed fromthe coagulum by passing it between rolls until the moisture content wasreduced to about 5%. The foregoing steps are disclosed in the abovementioned application of A. R. Kemp.

Raw balata blankets were cut into strips, and the strips were immersedin gasoline for about twelve hours, until about 90% of the resins wereextracted therefrom, after which they were dried. The weight of thebalata after leaching was equal to that of the rubber content of thecoagulum. The rubber and balata were then washed together for one hourin a rubber washer. In the present specification and claims, the termderesinated balata includes any balata gum the resin content of which issufliciently low to permit its use in this composition. It is possibleto secure a fairly satisfactory composition by using a good commercialgrade of balata without deresinating, but on account of the tendency ofthe resins to soften the rubber and impair the electrical stability ofthe product, a more or less thorough deresinationwill usually be foundadvisable.

Montan wax was then ground to the fineness of ordinary ground coffee,and refined by leaching with benzol for-"about ten hours, until thebenzol was no longer highly colored, about 20% byweight of the wax beingextrac'ted in this manner. 1 The remaining wax "truded about copperconductors to form cable cores inthe well known manner.

The cores formed as above described, and other cores formed of.insulating material containing the "same ingredients in varying"amounts, were immersed in water and tested to determine theirelectrical characteristics,- the tests being carried on over a period ofmonths to determine the deterioration, if any, due to the effect ofwater on the insulating material. The following tables show the resultsobtained in these tests, the corresponding values for a typicalgutta-percha cable being also, given for comparison. The values givenare the means'of various readings taken over an extended period of time,the specimens being tested at temperatures of about 75 F.,-atmosphericpressure, and subjected to an alternating current of 900 cycles persecond. T e outer diameter of eachcore was approximately 0.47" inches.

Capaci- Conductaupe in tilahioe in {3&889

mlcroeroer- Material 0! com larads mhos ggg a once per per angle innautical nautical radians mile mile Gutta-percha 379 22. 0 3. 0107 50%rubber, 50% balata,

a wax 254 3. 1 2. 60 .0022 45% rubber, 45% balata, r

10% wax 250, 0. 6 2. 58 0048 40% rubber, 40% balata,

20% wax .fi33 10.2 2.70 .0069 35% rubber, 35% balata, v

30% war .258 10.3 2.67 .0071

- Referring to the drawings, Fig. 1 shows comparative curves -A, B, Cand D plotted from data obtained from the test cores and showsthevariations in the conductance of the insulation when immersed in water.Curve A is inserted merely for purposes of comparison, and shows thebehavior of a typical high grade gutta-percha' such asis commonly usedin submarine cable cores. Curve B represents a core containing rubber,balata and Montan wax in-the pro ortions of 36%, 20%, 44%, wherein therubber and wax were treated as above noted but the balata was nottreated to remove the resins.

Curve G represents a core containing rubber,

balata and Mon tan wax in the proportionsof 35%, 30%, 35%, each of theingredients having been purified as above noted. Curve D represents acore containing deproteinized rubber and deresinated balata in equalproportions, with no wax. I

Fig. 2 shows'variations in the capacitance of the same cores, the curvesE, F, Grand H representing the results from cores correspondingrespectively with those upon which curves B, C and D of Fig. 1 arebased. From curves B and F the desirability of purifying the balata inevident, although it is apparent that the compound from which curves Band F were derived may be used where the requirements'are not tooexacting. Curves C and G illustrate the behavior of a satisfactorycompound, the electrical characteristics of which are at alltimessuperior to those of gutta percha, and are practicallyv unaffected byimmersion in water. Curves D and H show that a superior cornpoundmay bemade with rubber and balata alone, al

\ though the omission of the wax makes the unit price of the compoundhigher. Such a compound is fully disclosed in the copendingapplicationof Charles Martell, Serial No. 308,610, filed Sept. 27, 192 Ya It shouldbe noted thatthe above curves show the values at roomtemperature and atc nospheric pressure, and that when the cores aresubjected to the temperatures and pressures. existing at sea bottom theyshow a marked improvement regard to their electhe above dimensions'has aconductance of about 50 micromhos per nautical mile.

These curves, as well as the data given in i the above table,'show thatwith respect to each of the electrical characteristics measured in thetests, compositions made in accordance with this invention aredistinctly superior to gutta-percha. The time of treatment at anyparticular temperature, for any specific requirements, and for specificgrades of materials, at variance with those already described, must'beexperimentally determined. However, the specific procedure describedabove is typical of those'which produce materials having satisfactoryproperties.

The preferred proportions of the ingredicuts to each other are rubber,35%, balata 35%, and wax 30%, but these proportions may be variedconsiderably, depending upon the nature of the materials used, and thespe- V cific requirements of the insulator to be made. A ratio of rubber25%, balata 25 and wax 50% may be used for certain purposes where greattoughness and mechanical strength are not required, and a ratio ofrubber 45%, balata 45%, and wax 10% is satisfactory for most purposes,except that the unit cost of the composition increases with a decreasein the percentage'of wax.

In general, an increase in the proportion of Montan wax lowers the costand increases the thermo-plasticity and workability of the mixture, butproduces acomposition having tendency to cold flow. An increase in the;rubber content results in improved electrical qualities, but increasesthe cost and tends to make the composition too resilient to permitproperextr'usion to accurate dimensions in the cable-extrusion pressesnow in use'in the Ject to deformation at ordinary temperatures. Anincrease in the proportion of balata tends to prevent cold flow of thematerial and in-' creases its thermo-plasticity and toughness, 1 butincreases the cost of the'composition.

The product, if made in accordance with this specification, should be,in respect both to electrical and mechanical characteristics, superiorto gutta-percha, and at the present market, prices considerably cheaperthan gutta -percha. Tackinessmay be completely avoided and theelecrical'properties perfectly stabilized; Compositions may thus beobtained possessing characteristics which adapt J h 0 them to the moststringent requirements for submarlne cables. They are superior inelectrical characteristics to any materials previously used'for thepurpose and, in cpnjunc-.

tion with the development of modern loading materials, 'make possiblelong cables of reasonable dimensions, suitable for the transmission ofspeech frequencies, which heretofore have-been regarded as commerciallyunattainable. The" compound when heated to about 80 C. is sufiicientlyplastic to be extruded in the cable-extrusion presses now in use in theindustry. No vulcanization or other subsequent treatment is necessary.The specific gravity of the finished product is about 0.95.

It has been determined for Hevea rubber that a 'reduction in thenitrogen content (which is approximately proportional to the proteincontent) to one-half that in the corresponding commercial crude rubberresults in a satisfactory ingredient in submarine cable insulation.compounded in-accordance with this invention. It may be found that forsuch use a smaller reduction will sufiice,

or that for use in moist air or under less extreme conditions a stillsmaller reduction will be suificient to stabilize the electricalproperties of the product. It may also be found that the deleteriouseffect of the proteins may be avoided by coagulating them or otherwisemodifying them to render them harmless. The as used in the claims ofthis application, is therefore intended to include any rubber theprotein content of which has been so reduced or modified, or any naturalor synthetic rubher having a sufiiciently low protein content, as toproduce a composition having stabilized electrical properties.

Instead of Montan wax, other hard waxes or *other similar substances maybe used which .are fusible at moderate temperatures,

and which themselves possess suitable electrical characteristics and asuitable resistance to the penetration of water. Candelillaand carnaubawaxes and Montan pitch are examples of substances which may be used inplace of Montan wax.

Instead of balata, gutta-percha or other similar' gums may beused toincrease the toughness and plasticity of the material.

From the electrical data given above, it is apparent that thesecompositions are much better adapted as to electrical characteristicsfor insulation of conductors for high frequency transmission than isgutta-percha. Of importance in this connection are the low dielectriclosses in these compositions at speech or carrier frequencies. Thesmaller the power factor, and, therefore, the phase difference angle,the lower will be the dielectrio losses.

product and balata are term deproteinized rubberlnsulation, it isobvious that it has a more general application to insulating materialsand especially to such materials which may be subjected tothe'influenceof humidity or water. 0

What is claimed is:

1. An insulating material composed of balata, wax, and a productresulting from the treatment of rubber to remove the water absorbentsubstances, in which the rubber present in proportions of not more than45% each, the balance being commercial wax further refined.

2. An insulating material composed of approximately 35% deproteinizedrubber, 35% deresinated balata, and 30% commercial Montan wax furtherrefined.

3. An insulating material composed of approximately 35% deproteinizedrubber, 35% deresinated balata, and 30% commercial Montan wax furtherrefined, the ingredients being thoroughly mixed together to form ahomogeneous composition.

4. A composition of matter composed of approximately equal parts-ofdeproteinized rubber, balata, and commercial hard wax further refined.

5. An insulating material composed of approximately equal parts ofdeproteinized rubber and balata, the 'remainder being a commercial hardwax further refined.

6. A composition of matter composed of approximately equal parts ofdeproteinized rubber, deresinated balata, and commercial hard waxfurther refined.

7. A composition of matter composed of approximately equal parts ofdeproteinized than rubber and having properties similar to balata, and acommercial therm'o-plastic Montan lignite derivative further refined andimpervious to water.

10. A composition of matter composed of deproteinized rubberhydrocarbon, a purified gum exudate other than rubber and havingproperties similar to balata, and a commercial thermo-plastic Montanlignite derivative further refined and impervious to water.

11. An insulating material composed of deproteinized rubber hydrocarbon,a purified gum exudate other than rubber and havingproperties similar tobalata, and a commercial thermo-plastic Montan lignite derivativefurther refined and impervious to Water, the materialbeing characterizedby a lower dielectric constant than 'gutta-percha. 12. An insulatingmaterial composed of deproteinized rubber, balata, andcommercharacteristics superior to high-grade guttapercha andsubstantially unaffected by immersion in water for 200 days.

13. An article of manufacture consisting of deproteinized rubberhydrocarbon having low water-absorption characteristics, a purifiedvegetable gum other than rubber and having properties similar tobalata,- and a commercial plastic material further refined andimpervious to water.

14. An article of manufacture consisting of deproteinized rubberhydrocarbon having low-water absorption characteristics, a vegetable gumother than rubber and having properties similar to balata, and acommercial plastic material further refined.

15. The method of producing an insulating material from rubber, balata.and- Montan wax, which consists in rendering soluble the water-absorbingconstituents of the rubber. simultaneously washing and mixing the rubberand balata, adding the Montan wax to the mixture, and continuing themixing until a homogeneous product is obtained.

16. The method of producing an insulating material from rubber latex,balata, and wax, which consists in heat-treating the latex to rendersoluble the water-absorbent substances naturally present in thelatex,.coagulating the latex, adding balata thereto, simultaneouslywashing and mixing the rubber and balata, and adding wax to the washedmixture.

17. An insulating material consisting of rubber hydrocarbon having itsnitrogen content .reduced and being intimately commingled with balataand commercial Montan wax further refined.

18. An insulating material composed of 40 rubber treated for severalhours under a steam pressure at a temperature considerably above 100 C.thoroughly washed, dried and intimately commingled with balata and acommercial Montan lignite derivative further refined.

' In witness whereof, I hereunto subscribe my name this 14th day ofSeptember, .A. D.

1928. CHARLES MARTELL.

